1. Field of the Invention
This invention relates generally to electrical communication systems and more particularly to a communication system that processes and reformats real time analog video or digital message signals, received concurrently from multiple sources, into a sequence wherein no information is lost due to overlap or masking.
2. Description of Related Art
It is well known that in certain types of electrical communication systems, for example, systems which receive voice messages which overlap one another such as might be experienced by an aircraft dispatcher, some or part of one of the messages, typically the first message, is lost. It may be a key word or two or it may be several seconds of an important message that may be missed, with some very undesirable consequences resulting therefrom.
For example, in a real-time voice communication system where an air traffic controller is communicating with multiple aircraft on multiple frequency channels, the controller may receive an interfering message which is superimposed on an incoming transmission to which the controller is already listening. At the conclusion of the incoming transmission, the first message is resumed, but part of it has been lost.
Another example is where a dispatcher is receiving a voice transmission from a mobile unit, such as a police car or an ambulance. When a second unit transmits a message concurrently with the first received message, the second message is superimposed on the first and again, part of the first message may be lost.
Yet another example is where a hearing, such as a congressional or other type of hearing, is being conducted and broadcast. While testimony is being given, an announcer often must interject comments, such as who the speaker is or what is coming next, or simply to interject a station or network identification break. As a result, important comments may be lost because of the undesired disruption in the broadcast.
In all of these instances, information is undesirably lost to the detriment of the listener.
Accordingly, it is an object of the invention to provide a communication system which concurrently process real-time information signals from multiple sources without a loss of information.
It is another object of the invention to provide a communication system which shifts incoming messages in near real-time as required to prevent overlap.
It is still a further object of the invention to provide a parallel to sequential message converter which automatically reformats superimposed messages in either digital video or analog communication channels to a sequential format and gradually returning to real-time transmission.
These and other objects are achieved by a parallel to sequential message converter including: a pair of signal input ports for receiving a first input signal having a duration of a first time period and a second input signal having a duration of a second time period, the second time period being less than the first time period, and wherein the second input signal is received concurrently with a portion of the first input signal so that a time overlap in signals exists; a signal output port; means for coupling the first input signal to the signal output port; means for delaying the first input signal at the onset of the second input signal for a period substantially equal to the second time period of the second input signal; and, means for coupling the second input signal to the signal output port at the start thereof and thereafter coupling the delayed first input signal to the output port so as to provide a sequential output of said first and said input signals without a loss of any portion of the first input signal.
The delay of the first input signal is provided by a refresh buffer memory having a controllable read out command and read out speed, and being operable such that the first message signal is read out of the memory at the end of the second message signal at an increased readout rate. In another aspect of the invention, the readout rate is increased through a frequency decimation method where both the first and second input signals are digitized, stored and sequentially combined. The output rate of the stored first input signal is increased by passing it through a decimation filter which comprises the bandwidth of the signal and then resamples the signal to reduce the total number of samples in the output so that when it is reproduced the bandwidth is restored.
Further scope of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood, however, that the detailed description and specific examples indicating the preferred embodiments of the invention are provided by way of illustration only, since various changes and modifications coming within the spirit and scope of the invention will become apparent to those skilled in the art from the detailed description.